1. Technical Field of the Invention
This invention relates to radio telecommunication systems and, more particularly, to a system and method of simultaneously transmitting voice and data in a digital radio telecommunications network.
2. Description of Related Art
There are several methods for providing simultaneous voice and data in the prior art, but the methods address the problem strictly from a landline perspective. Additionally, some landline methods are based on the Integrated Services Digital Network (ISDN) which utilizes entirely different channels for voice and data. ISDN is not really applicable to mobile telephony. In addition, ISDN solutions have the disadvantages of high access and equipment prices, and the lack of an ubiquitous ISDN service offering.
Digital landline modems capable of simultaneously transmitting voice and data are known as Digital Simultaneous Voice and Data (DSVD) modems. There is also an analog version called Analog Simultaneous Voice and Data (ASVD). When incompatible competing products began to appear on the market, a standards group called TR.30 began to develop a set of standards for digital landline modems.
A DSVD modem works on one channel and multiplexes the voice and data traffic. The DSVD modem takes a voice signal and digitizes and compresses it (i.e., encodes it) in an 8-kilobit bandwidth with a speech encoding algorithm in a digital codec. As required, data traffic utilizes the remainder of the available bandwidth on the channel. The TR.30 standards also provide for Voice Activity Detection (VAD) which continuously determines whether there is any voice activity on the channel. If there is no voice activity, then most of the modem bandwidth is reallocated to the sending of data during the gap in voice activity. When voice activity resumes, some of the bandwidth is reallocated to the transmission of voice. For example, if a system is operating with a 28.8 kilobits per second (kbps) (V.34) modem, voice traffic may utilize 8 kbps while data utilizes 14.4 kbps. When the user stops talking, the rate for data jumps to 28.8 kbps. When the users starts talking again, the data rate falls back to 14.4 kbps. DSVD modems may be utilized for such applications as collaborative conferencing (e.g., shared whiteboard or image/document sharing), remote presentations, remote terminal viewing, games, entertainment, home shopping, and simultaneous faxing.
However, because of the optimized speech compression utilized in digital cellular networks, a modulated DSVD signal cannot be directly passed through the digital cellular codec without significant impairment. Therefore, other solutions are required. DSVD and ASVD modems exist for landline communication systems only. Mobile subscribers do not have the ability to simultaneously transmit voice and data through a DSVD modem. From the perspective of mobile communications, systems utilizing Code Division Multiple Access (CDMA) may have a simultaneous voice and data service that supports the sending of packet data along with voice, but the CDMA specifications do not address the inoperability with DSVD. CDMA does not teach or suggest a method of transmitting simultaneous TR.30 circuit mode data and voice. The Global System for Mobile Communications (GSM) system does not provide simultaneous voice and data service on a single channel, but allows a user to switch between a voice mode and a data or fax mode without hanging up. Thus, if two subscribers are talking, they can do a service switch, or service change to another mode such as a data or fax mode, send a fax, and then revert back to conversation mode.
Although there are no known prior art teachings of a solution to the aforementioned deficiency and shortcoming such as that disclosed herein, U.S. Pat. No. 5,553,063 to Dickson (Dickson) and an IEEE article by Brown and Feher, "A Reconfigurable Modem for Increased Network Capacity and Video, Voice, and Data Transmission over GSM PCS" (Brown et al.) discuss subject matter that bears some relation to matters discussed herein. Dickson discloses a system for full duplex real time two-way voice and data communication between a pair of computer terminals. However, the system of Dickson is strictly a landline system, and there is no teaching or suggestion of a system which simultaneously transmits voice and data in a digital radio telecommunications network either by utilizing existing IS-136 standards and network nodes, or by interworking DSVD modems within the nodes of the network.
Brown et al. disclose a reconfigurable modem interface compatible with the GSM system which doubles the number of simultaneous video and voice transmissions per channel. However, Brown et al. describe a complex implementation utilizing half-rate voice coding based on a modified vector sum excited linear prediction (VSELP) algorithm, and utilizing variable rate codecs. Brown et al. do not teach or suggest a system which simultaneously transmits voice and data in a digital radio telecommunications network either by utilizing existing IS-136 standards and network nodes, or by interworking DSVD modems within the nodes of the network, thereby providing a simple implementation suitable for simultaneous voice and moderate data requirements.
Review of each of the foregoing references reveals no disclosure or suggestion of a system or method such as that described and claimed herein.
In order to overcome the disadvantage of existing solutions, it would be advantageous to have a system which interworks DSVD modems with a cellular radio system in a simple implementation suitable for simultaneous voice and moderate data requirements. The present invention provides such a system. The present invention also simultaneously transmits voice and data in a digital radio telecommunications network by utilizing existing IS-136 standards and network nodes. Additionally, ASVD modems may be utilized for analog transmissions.